It is important to the operation of a paper machine that all the papermaking fabrics remain clear of contamination, which would impede the drainage of the wet paper sheet. Papermaking fabrics include forming fabrics, wires, press fabrics, conveying belts, and any fabric that is used either as a drainage element on a paper machine or used to impart molded properties to a sheet of paper including fabrics used in through-air-drying (TAD) processes. This may also include fabrics used in drying paper such as dryer felts. In addition papermaking rolls may be subject to contamination. These rolls may or may not contact the surface of a paper sheet. In either case contamination on the surface of these rolls may impede the ability to operate a papermachine effectively or may cause quality defects in the paper itself. Papermaking rolls could include press rolls, suction rolls, transfer rolls, felt carrying rolls, tension rolls. Contamination may also occur on other surfaces of a paper machine including uhle box covers, foils, molding boxes, pickup shoes, etc. This contamination can occur in many forms and may consist of a variety of inorganic scales and deposits as well as organic materials which may include naturally derived wood pitch, lignins, and small diameter wood derived cellulosic materials commonly called “fines”. Additional contaminants include synthetic materials including various types of adhesives, paper additives such as sizing agents including alkyl ketene dimer (AKD), alkyl succinic anhydride (ASA) and rosin sizes, latexes, wet and dry strength additives and polymers. Many of these types of materials naturally exist and are commonly added to the papermaking stock to impart certain desirable properties to the final paper sheet or to aid in the processing of the paper sheet during manufacture on the paper machine.
In the area of tissue manufacture, additional additives are used which impart properties such as softness, wet strength and dry strength. These additives may be added into the papermaking stock prior to the paper machine or they may be added during the pressing stage. These additives include polymeric strength additives, such as polyaminoamidoepichlorohydrin, polyvinylamines, imidazolines, anionically stabilized dispersions, oil and wax emulsions, and dispersions either anionically or nonionically stabilized, fatty acids and triglycerides and derivatives thereof. These additives may also be added onto the surface of the drying can during the drying stage of tissue paper manufacture. Additionally, these additives may be used to change the surface properties of the sheet as well as the behavior of the paper sheet in the creping process which uses a blade to scrape the paper sheet from the surface of the drying can.
In addition, recycled paper and paper fibers used as a component of the papermaking slurry often contain a variety of deleterious contaminants including, but not limited to, adhesives, waxes, sizes, strength additives, oils, and materials commonly referred to as “stickies”.
Currently, a variety of treatments are used to prevent the deposition of contaminants on paper machine fabrics. These treatment methods include surfactants, which normally consist of anionic, nonionic and cationic low molecular weight molecules. The surfactants function primarily by emulsifying or dispersing existing contamination in the paper machine fabric. In addition, a variety of polymers has been used to prevent contamination. These polymers are typically cationic in nature. They function primarily by passivating papermaking surfaces. and preventing the deposition of contaminants on those surfaces. In one instance, the utility of these polymers is limited due to their tendency to accumulate on the papermaking fabric fibers and cause a decrease in the papermaking fabric performance. The decrease in the papermaking fabric performance is typically a result of plugging the pores and the void volume of the paper machine fabric. In another instance, the utility of the cationic polymers is limited by the fact that they are consumed by anionic components in the papermaking slurry or furnish thereby reducing their effectiveness or forming tacky reaction products.
Terephthalic based polymers based on the copolymer polyethylene terephthalate: polyoxyethylene terephthalate (PET:POET) have also been used to prevent the deposition of organic deposits on papermaking fabrics. These polymers have an affinity for the surface of press fabrics and prevent the deposition of organic contaminants on their surface. However, usage rates tend to be higher and their efficacy is diminished because they have a lower persistence on papermachine fabrics and may rinse out more easily. In addition the effectiveness of these polymers may be diminished by dissolved materials in the papermaking furnish which may either interfere with the adsorption of the PET:POET or their derivatives onto the papermaking surface.
Accordingly, a method of effectively controlling deposits on papermaking fabrics on paper machines is desired.